To control supplying of compressed air to a pneumatic equipment or the like, or to control compressed air exhaust from the pneumatic equipment, or further to control a process to switch communication passages, a solenoid valve which uses a poppet valve to open and close communication holes provided in a valve seat has been utilized.
In a two-port solenoid valve having an air-supply port communicating with a compressed air-supply source and an output port communicating with an equipment to be supplied with compressed air, a poppet valve controls switching between a communicating state and a blocked state of the ports. On the other hand, in a three-port solenoid valve having an exhaust port in addition to the air-supply port and the output port, the poppet valve controls switching between two states. In one state, the poppet valve operates to block communication between the exhaust port and the output port while enabling communication between the air-supply port and the output port, thereby supplying compressed air to the pneumatic equipment through the output port. In the other state, the poppet valve operates to block communication between the air-supply port and the output port while enabling communication between the exhaust port and the output port, thereby discharging the compressed air, which returned to the output port from the pneumatic equipment, to the outside through the exhaust port.
A solenoid which opens and closes the poppet valve has a fixed iron core with a magnetic wire wound around, and a movable iron core to be driven by the magnetic wire, that is, an energized coil; thus, a poppet valve is driven by the movable iron core. The movable iron core is a swingable type which is swingable about one end portion of the movable iron core; this swingable movable iron core is also referred to as a “flapper” or an “armature”. Patent Documents 1 to 3 describe such solenoid valves each having a swingable movable iron core.